Update build configs for multiple rockchip platforms

This is needed to support compiling new source file in TF-A which
adds support for stack protection.
Also updated the default tf-a build configs for these 4 platforms:
1. rk3328
2. rk3368
3. rk3399
4. px30

Signed-off-by: Madhukar Pappireddy <madhukar.pappireddy@arm.com>
Change-Id: Ia7921a21f83edead9e3f4c61b1f45b9781d2e039
diff --git a/tf_config/rk3399-default b/tf_config/rk3399-default
index 9a27e0c..56cee02 100644
--- a/tf_config/rk3399-default
+++ b/tf_config/rk3399-default
@@ -1,2 +1,3 @@
 CROSS_COMPILE=aarch64-none-elf-
+ENABLE_STACK_PROTECTOR=strong
 PLAT=rk3399